Various devices can be installed in a well traversing a hydrocarbon-bearing subterranean formation. Some devices control the flow rate of fluid between the formation and tubing, such as production or injection tubing. An example of these devices is an autonomous fluid selector that can select fluid, or otherwise control the flow rate of various fluids into the tubing.
An autonomous fluid selector can select between desired and undesired fluids based on relative viscosity of the fluids. For example, fluid having a higher concentration of undesired fluids (e.g. water and natural gas) may have a certain viscosity in response to which the autonomous fluid selector directs the undesired fluid in a direction to restrict the flow rate of the undesired fluid into tubing. The autonomous fluid selector includes a flow ratio control assembly and a vortex assembly usable to select fluid based on viscosity. The flow ratio control assembly includes two passageways. Each passageway includes narrowed tubes that are configured to restrict fluid flow based on viscosity of the fluid. For example, one tube in the first passageway may be narrower than the second tube in the second passageway, and configured to restrict fluid having a certain relative viscosity more than fluid having a different relative viscosity. The second tube may offer relatively constant resistance to fluid, regardless of the viscosity of the fluid.
Although this autonomous fluid selector is very effective in meeting desired fluid selection downhole, additional types of autonomous fluid selectors are desirable that can select fluid based on relative viscosity, or select fluid based on one more other fluid properties, such as fluid density, or fluid velocity.